It is well known in the art that polymeric hydrocarbon resins are usually made using a non-continuous batch process. It is also well known in the art that recycle or the retention of already formed product resin in a batch reactor during a living thermal polymerization process will have an effect on the final product properties such as increasing the molecular weight as measured by Mz. Recycle is also used in the art for separating component/solvent mixtures, assisting in distillation and product recovery, and for removing unreacted materials. The batch process is slow and labor intensive, however. The batch process requires long preheating periods as well as long fill and drain times. Also, the batch process typically yields only 65% resin product. These factors lead to a high monetary cost for running a batch process. Consequently, the art needed a way to obtain polymerizate in a faster and more cost efficient manner. This need was partially met by the continuous polymerization process. Indeed, it is known in the art that a continuous process reactor can make a large variety of hydrocarbon resins. The benefits, inter alia, are that the same amount of product can be obtained in a shorter time period using smaller equipment. The most noteworthy benefit is the reduction in time required in the reactor. This time reduction is directly related to reducing costs.
The art, however, does not as yet have a continuous means to vary specific product properties of product obtained by living thermal polymerization. Living thermal polymerization is polymerization without catalyst, i.e. heating the thermally polymerizable feed will cause the reactants to polymerize. It is also recognized that an ability to control product properties, such as selectively varying Mn, Mz and Mw, is a highly desirable aspect. It is an object of this invention to provide a continuous thermal polymerization process wherein recycle of product back into the reactor at any point is used to control and selectively increase the product properties especially the mole weight as measured by Mz, Mz being the measure of higher molecular weight materials.
M.sub.w is the weight average molecular weight, M.sub.n is the number average molecular weight and M.sub.z is z-average molecular weight. M.sub.n is generally the measure of the number of molecules present in a sample of interest. (i.e., M.sub.n =total weight of sample divided by number of molecules). M.sub.w is generally a measure of the mass of the sample of interest and is the second power average of molecular weight. M.sub.z is the third power average of molecular weight in a polydisperse polymer.